Common metalization schemes for silicon based integrated circuits comprise multilayer contact structures. Such structures typically include aluminum or aluminum/copper metalization layers serving as electrical conductors. The semiconductor devices in such circuits require protection against aluminum or aluminum/copper interdiffusion or spiking into the silicon substrate. Further, silicon based devices require protection against mobile ion contamination.
The present invention relates to providing protection against both the aluminum or aluminum/copper spiking and against mobile ion contamination. The present invention provides this protection while allowing normal processing to be done on multilayer metal structures.
Specifically the present invention comprises a bimetal layer located between two portions of an integrated circuit, the bimetal layer comprising a layer of TiWN and a layer of TiN.
Prior art disclosures separately address the nitriding of TiW or Ti as a barrier metal against spiking, and also separately address the possibility of using Ti as a barrier against mobile ion contamination. However, the reaction of Ti with Si has prohibited the use of Ti alone. The present invention uses TiN instead of Ti and adds TiWN to satisfy both requirements.